Peter Hain set out his stall for Labour's deputy leadership today with commitments to narrow the gap between rich and poor and to "tell it straight" to Gordon Brown.

As the race for John Prescott's job hots up, Mr Hain said he would be a "strong voice" for Labour in the cabinet, and promised to be loyal to the prime minister-elect, but frank in his advice.

"As you all know, I've never been afraid to speak my mind, to tell it straight," he said.

Mr Hain rejected the suggestion by fellow MP Margaret Hodge that established families in Britain should take housing priority over immigrants. Allocation should be carried out according to need, he said.

Mr Hain warned that Labour had its "work cut out" to win the next election, arguing that "more of the same" would not be enough to put the party on course for victory.

He called for a new "red-green" agenda of environmental protection and social justice, and said that there had to be "much more action" to narrow the rich-poor divide.

Mr Hain's hopes for the deputy leadership were boosted today by the endorsement of a third affiliated trade union. Construction union Ucatt - Labour's seventh largest affiliate - has joined Aslef and the Bakers, Food and Allied Workers Union in endorsing Mr Hain to members who will have a say in the three-way electoral college vote.

The new superunion Unite - comprised of Amicus and the T&G - has meanwhile thrown its weight behind backbencher Jon Cruddas, handing over £30,000 to his campaign coffers.

Mr Cruddas, seen as the candidate of the left, braved criticism of Labour policy at a hustings staged yesterday in Coventry.

The MP for Dagenham was the only one of six deputy leadership contenders to call for a moratorium on the use of private contracts to deliver NHS services.

Mr Cruddas followed this up today by launching an outspoken attack on Tony Blair's flagship city academies and trust schools programmes which he said had failed to improve standards and are creating a "two-tier" system.

Mr Cruddas told an education conference: "We need to take a long, hard look at where academy and trust schools are taking us and whether, far from giving 'choice', they are deepening social divisions."

Meanwhile, Hilary Benn's deputy leadership campaign team claimed an early success for the international development secretary today.

They said that Mr Benn had more "friends" on his online Facebook profile than any other candidate.

Mr Benn has 560 supporters on the networking site, compared with 269 for Alan Johnson, 226 for Hazel Blears, 201 for Mr Cruddas, 143 for Mr Hain and 136 for Harriet Harman.

Mr Benn's campaign chairman, Ian McCartney, said: "The vote that matters will be the ballot of party members and trade unionists, but we know that the grassroots trust Hilary to be a voice for the thing they care about."

Meanwhile, Ms Blears will use a hustings event tonight to call for a four-fold increase in the number of ethnic minority politicians in the UK.

Only 15 of the 646 MPs in the Commons at present are black or Asian: two Tories and 13 Labour.

Speaking at the Black Socialist Society meeting in Westminster, the party chair is expected to pledge to act to meet the target if elected.

"Let me say at the outset how important it is that our modern party reflects our modern society," she will say.

"We need more BME [black and minority ethnic] candidates and elected representatives, including in town halls, in parliament, in the cabinet.